1. Field of Invention
This invention relates to confocal microscopic equipment that can measure the solid shape of a sample at high speed; and more particularly, to equipment that does not require scanning of an irradiating beam.
2. Description of the Prior Art
The confocal microscopic equipment has resolution in the direction of an optical axis as well as resolution on a sample surface by scanning the irradiating beam on the sample and detecting light reflected from the sample through a pinhole or slit. The resolution in the direction of the optical axis obtained by detecting light through a slit is described in "Three-dimensional optical transfer function analysis for a laser scan fluorescence microscope with an extended detector" by S. Kawata, R. Arimoto, and O. Nakamura, J. Opt. Soc. Am. A. Vol 8, No. 1, (1991).
FIG. 1 shows a conventional confocal microscopic equipment, wherein an output light beam from laser 1 is made incident to galvo-scanner 2 and then a reflected beam from galvano-scanner 2 is made incident to beam splitter 4 via mirror 3. Beam splitter 4 reflects the incident beam from galvano-scanner 2 and makes the reflected light irradiate sample 6 via objective lens 5. The reflected light from sample 6 is again made incident to objective lens 5 and then made incident to one dimensional charge coupled device (CCD) camera 7 via beam splitter 4.
The operation of the FIG. 1 equipment will be described with reference to FIG. 2, which refers to each pixel of CCD camera 7. The output beam of laser 1 is scanned by galvano-scanner 2 and directed to scan sample 6 in a one dimensional direction. The reflected beam from sample 6, scanned in a one dimensional direction, is made incident to CCD camera 7. In CCD camera 7, the reflected beam scanning direction is set to match the direction marked "A" in FIG. 2. For example, the reflected beam is detected, for example, in turn with the pixels marked "B", "C", and "D" in FIG. 2. In this case, since each pixel can detect the reflected beam only in the range of the height of pixel marked "E" in FIG. 2, this means that the pixels detect substantially only the reflected beam that has passed through a slit of width "E".
That is to say, if it is assumed that the direction of the optical axis is the z-axis, the plane orthogonal to the optical axis is the x-y plane and the direction of scanning is the x-axis, then the equipment has resolution which is also in the z-axis direction. Thus, the fault shape of the x-z plane can be measured by scanning sample 6 in the z-axis direction. In addition, measurement of the solid shape of the sample 6 is made possible by scanning sample 6 in the z-axis direction while moving sample 6 in the y-axis direction in turn.
As a result, the resolution in the direction of the optical axis as well as the resolution on the sample surface can be obtained by scanning a laser beam in a one dimensional direction and by detecting the reflected light with a one dimensional line CCD camera 7.
However, there are problems one encounters when using conventional equipment in that expensive optical equipment such as a laser 1 is necessary and a scanning means such as a galvano-scanner 2 is required.
Moreover, there are other problems. For example, the wavelength becomes longer and the resolution worsens because the laser incorporated in the confocal microscopic equipment can be used only in a red color system due to size and price. Also, since the laser beam is a coherent light beam, speckle noise is generated , which degrades the signal to noise ratio (S/N).